1. Field of the Invention
The present invention relates to a differential limiting apparatus, and more particularly relates to the differential limiting apparatus having a clutch restricting a differential movement of a differential mechanism.
2. Description of the Prior Art
It is well known for a prior differential limiting apparatus to restrict a differential movement of the differential apparatus by connecting between an input shaft and an output shaft of a pair of output shafts, as disclosed in published patent document Tokkai 2007-138983.
This conventional differential limiting apparatus includes a housing rotated with an input shaft, a differential mechanism distributing differentially a rotating force from the housing, a clutch restricting a differential movement of the differential mechanism and a driving mechanism driving the clutch.
The housing includes a front housing comprising a hollow cylindrical body having a bottom and opening to one direction, a rear housing comprising an annular cylindrical body provided on the opening of the front housing. The housing is connected to the input shaft and constructed to rotate by receiving a driving force from a driving source such as an engine of a vehicle.
The differential mechanism includes a ring gear as a pair of output gears respectively connected to the pair of output shafts, a sun gear, planetary gears engaged in mesh with the ring gear and the sun gear. The differential mechanism is accommodated in the housing and constructed to distribute a rotational force from the housing to a pair of the output shafts differentially.
The clutch includes a plurality of outer clutch plates and a plurality of inner clutch plates and the clutch is disposed between an inner surface of the housing and an outer surface of the ring gear. The clutch is constructed to connect the input shaft and one output shaft in order to restrict the differential movement of the differential mechanism when the plural outer clutch plates and the plural inner clutch plates are engaged by friction. The plural outer clutch plates are engaged by spline engagement with the inner surface of the front housing and the plural inner clutch plates are engaged by spline engagement with the outer surface of the ring gear. Each of the plural outer clutch plates and each of the plural inner clutch plates are disposed alternatively with each other.
The driving mechanism includes an electromagnetic clutch, a pilot clutch driven by receiving an electromagnetic force from the electromagnetic clutch, and a cam mechanism transforming a rotational force from the housing to a pushing force toward a main clutch by driving the pilot clutch. The driving mechanism is disposed around peripheries of a pair of output shafts inside the housing. The pushing force is transmitted via a cylindrical portion to a bottom portion of a cylindrical output transmitting member having the bottom portion and a cylindrical portion, and after that transmitted via the cylindrical portion of the output transmitting member to the main clutch in order to connect the outer clutch plates and the inner clutch plates by friction.
In the above-mentioned construction of the prior art, when the driving force from an engine is input into the housing through the input shaft, the housing is rotated around the rotational axis. Upon the rotation of the housing, the rotational force is transmitted to the planetary gear, and after that from the planetary gear to the ring gear and the sun gear. Since the ring gear and the sun gear are respectively connected to each of the output shafts, the driving force from the engine is distributed differentially according to a state of the driving of the vehicle and the differentially distributed torque is transmitted to the right and left output shaft.
In this stage, when the electromagnetic clutch is energized, the pilot clutch starts to be driven by the electromagnetic force of the electromagnetic clutch. At this time, the rotational force of the housing is transformed to a pushing force by the cam when the rotational force from the housing is received by the cam at the driving stage of the pilot clutch. The pushing force is exerted from the output member to the main clutch through the output transmitting member. Then the outer clutch plates and the inner clutch plates relatively approach one another to be contacted by friction, whereby the housing and the ring gear are connected, that is to say the input shaft and the output shaft corresponding to the ring gear are connected to be able to transmit the rotational force so that the differential movement is restricted.
However, in the differential limiting apparatus of the published patent document of Tokkai 2007-138983 as the prior art, it is necessary for the conventional differential limiting apparatus to increase a number of the clutch plates in order to obtain the larger differential limiting force, resulting in a bigger longitudinal size of the whole apparatus if a longitudinal length of the main clutch is longer than a longitudinal length of the planetary gear and a longitudinal length of the flange portion of the ring gear. As a result, a number of the outer clutch plates and the inner clutch plates are limited so that a capacity of the clutch is limited, whereby a sufficiently large differential limiting force cannot be obtained.